Mode Conditioning Question

[Patrick McHenry]

I'm trying to connect a access switch to our core switches. From what I have read, GLC-SX gbics can go a distance of 1800 feet using 50 micron multi-mode fiber. I can't cover this distance with GLC-SX gbics because we have a connecting segment that is using 62.5 micron multi-mode fiber.

So..I'm thinking I will use GLC-LX gbics. With LX gbics, Cisco recommends using a mode conditioning patch cord. And there are different patch cords for gbics that are connecting to 50 micron and 62.5 micron.

My question is this:

Since I have a mix of micron size over the path between the access switch and core switches, will this be a problem? Is there another solution?

See document attached

Thanks, Pat.

[jonathanaxford]

Hi Patrick,

My understanding is that you need a mode conditioning cable when using an LX GBIC on a 62.5 MM fibre, as it correctly aligns the signal for transmission across the medium.

Looking at your diagram (Best one i've seen on here by the way!) I would say that you will defo need a mode conditioning patch lead on the devices that terminate directly into the 62.5 fibre. BUT i think you may have some more serious issues to deal with - it looks like you have a 50um fibre being patched directly into a 62.5um fibre, which is likley to cause problems.

I am not sure whether a mode conditioning cable can be used at the passive patch point in order to remedy this? Maybe someone here will be able to advise.

By having two different diameters of fibre in the path there is a high chance of packet loss on the conneciton. Is there anyway you can either investigate changing the fibre so that the diameters match, or using another switch at the passive patch point to terminate each connection into?

Hope this helps

Jonathan

[Patrick McHenry]

Jonathon,

Thank you for your response. We do have two switches at the passive patch point and that is were the desparate switch connects to the network at the moment. I was trying to create a separate and redundant paths for the switch directly to the cores. Looks like I will have to live with the current set up.

That being said, I was wondering the same thing about putting another MCP between the passive patch panels. I was wondering if that would bring it back to 50um and allow it to carry on to the core?

The documentation on this stuff is a little confusing. One more question:

If there was a 50um fiber running from the switch to the cores, would I still need a MCP from the gbic to the first path panel or is that only if I have 62.5um?

Thanks,

Pat.